Pyridine derivatives

ABSTRACT

The invention relates to pyridine derivatives of the formula I ##STR1## wherein R 1 , A 1 , E 1 , n, A 2 , Z 2 , X and Y have the meaning given in claim 1.

SUMMARY OF THE INVENTION

The invention relates to pyridine derivatives of the formula I ##STR2##wherein R¹ denotes alkyl with up to 12 carbon atoms wherein one or twonon-adjacent CH₂ -groups may also be replaced by --O--, --O--CO--,--CO--O-- and/or --CH═CH--,

Y is F, Cl, --CF₃, --OCF₃ or --OCF₂ H,

A¹ and A² in each case independently of one another aretrans-1,4-cyclohexylene, wherein one or two non-adjacent CH₂ -groups mayalso be replaced by --O-- and/or --S--, or 1,4-phenylene which isunsubstituted or substituted by one or more halogen atoms and/or nitrileand/or CH₃ groups, and wherein one or more CH groups may also bereplaced by N,

Z¹ and Z² in each case independently of one another are --CH₂ CH₂ --,--CO--O--, --O--CO--, --CH₂ O--, --OCH₂ --, --C.tbd.C-- or a singlebond,

X is H, or in case of Y=F or Cl, also F and

n is 0, 1 or 2,

and also to liquid crystalline media being a mixture of at least 2compounds, characterized in that at least one compound is a pyridinederivative according to formula I.

The invention was based on the object of discovering new stable liquidcrystal or mesogenic compounds which are suitable as components ofliquid crystalline media and, in particular have advantageous values ofoptical and dielectric anisotropy, in particular for the value of Δε/ε⊥,combined with high nematogenity.

Similar pyridine compounds with cyano as the terminal group instead offluoro or chloro atoms or --CF₃ groups are, for example, described in EP0194153.

It has now been found that pyridine derivatives of the formula I arehighly suitable as components of liquid crystalline media. Inparticular, they have advantageous values of optical and dielectricanisotropy and especially advantageous low values of Δε/ε⊥. A smallratio of Δε/ε⊥ has an important influence on the electroopticcharacteristics of TN liquid crystal cells.

It is also possible to obtain stable liquid crystal phases with a broadnematic mesophase range including a good deep temperature behaviour anda comparatively low viscosity with the aid of these compounds.

Depending on the choice of the substituents, the compounds of theformula I can be used as the base materials from which liquid crystalmedia are predominantly composed; however, it is also possible forcompounds of the formula I to be added to liquid crystal base materialsof other classes of compounds, for example in order to influence thedielectric and/or optical anisotropy and/or the viscosity and/or thenematic mesophase range of such a dielectric.

The compounds of the formula I are colourless in the pure state and areliquid crystalline in a temperature range which is favourable placed forelectrooptical use. They are very stable towards chemicals, heat andlight.

The compounds of the formula I are further highly useful as startingmaterial for the preparation of liquid crystalline compounds having thestructural element ##STR3##

The invention thus relates to the pyridine derivatives of the formula I,to liquid crystalline media with at least two liquid crystallinecompounds, wherein at least one component is a compound of the formula Iand to liquid crystal display devices containing such media.

Above and below R¹, Y, A¹, A², Z¹, Z², n and X have the meaningindicated, unless something else is specifically stated.

For the sake of simplicity in the following, Phe is a 1,4-phenylenegroup which may be substituted by one or more halogen atoms and/or CNand/or CH₃ groups, Cyc is a trans-1,4-cyclohexylene group, Dio is a1,3-dioxane-2,5-diyl group, Dit is a 1,3-dithian-2,5-diyl group, Pyd isa pyridine-2,5-diyl group and Pyr is a pyrimidine-2,5-diyl group. PydXdenotes the group ##STR4##

The compounds of the formula I accordingly also include compounds of thepartial formulae Ia to Ib (having two rings), Ic to If (having threerings) and Ig to In (having four rings):

    ______________________________________                                        R.sup.1 --A.sup.2 --PydX--Y Ia                                                R.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y                                                                     Ib                                                R.sup.1 --A.sup.1 --A.sup.2 --PydX--Y                                                                     Ic                                                R.sup.1 --A.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y                                                           Id                                                R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --PydX--Y                                                           Ie                                                R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y                                                 If                                                R.sup.1 --A.sup.1 --A.sup.1 --A.sup.2 --PydX--Y                                                           Ig                                                R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --A.sup.2 --PydX--Y                                                 Ih                                                R.sup.1 --A.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --PydX--Y                                                 Ii                                                R.sup.1 --A.sup.1 --A.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y                                                 Ij                                                R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --PydX--Y                                       Ik                                                R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y                                       Il                                                R.sup.1 --A.sup. 1 --A.sup.1 --Z.sup.1 --A.sup.2 --Z.sup.2 --PydX--Y                                      Im                                                R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --Z.sup.2           --PydX--Y                   In                                                ______________________________________                                    

Among these, those of the formulae Ia, Ib, Ic, Id, Ie, Ih, Ii, Ik and Ilare particularly preferred.

The preferred compounds of the partial formulae Ia include those of thepartial formulae Iaa to Iad:

    ______________________________________                                        R.sup.1 --Phe--PydX--Y  Iaa                                                   R.sup.1 --Cyc--PydX--Y  Iab                                                   R.sup.1 --Pyd--PydX--Y  Iac                                                   R.sup.1 --Pyr--PydX--Y  Iad                                                   ______________________________________                                    

Among these, those of the formulae Iaa and Iab are particularlypreferred.

The preferred compounds of the partial formula Ib include those of thepartial formulae Iba to Ibj:

    ______________________________________                                        R.sup.1 --Phe--C.tbd.C--PydX--Y                                                                         Iba                                                 R.sup.1 --Cyc--C.tbd.C--PydX--Y                                                                         Ibb                                                 R.sup.1 --Phe--CO--O--PydX--Y                                                                           Ibc                                                 R.sup.1 --Cyc--CO--O--PydX--Y                                                                           Ibd                                                 R.sup.1 --Phe--CH.sub.2 CH.sub.2 --PydX--Y                                                              Ibe                                                 R.sup.1 --Cyc--CH.sub.2 CH.sub.2 --PydX--Y                                                              Ibf                                                 R.sup.1 --Phe--CH.sub.2 O--PydX--Y                                                                      Ibg                                                 R.sup.1 --Cyc--CH.sub.2 O--PydX--Y                                                                      Ibh                                                 R.sup.1 --Pyd--Z.sup.2 --PydX--Y                                                                        Ibi                                                 R.sup.1 --Pyr--Z.sup.2 --PydX--Y                                                                        Ibj                                                 ______________________________________                                    

Among these, those of the formulae Iba, Ibb, Ibc, Ibd and Ibe areparticularly preferred.

The preferred compounds of the partial formula Ic include those of thepartial formulae Ica to Ich:

    ______________________________________                                        R.sup.1 --Cyc--Cyc--PydX--Y                                                                            Ica                                                  R.sup.1 --Phe--Phe--PydX--Y                                                                            Icb                                                  R.sup.1 --Dio--Phe--PydX--Y                                                                            Icc                                                  R.sup.1 --Dit--Phe--PydX--Y                                                                            Icd                                                  R.sup.1 --Cyc--Phe--PydX--Y                                                                            Ice                                                  R.sup.1 --Phe--Pyd--PydX--Y                                                                            Icf                                                  R.sup.1 --Phe--Pyr--PydX--Y                                                                            Icg                                                  R.sup.1 --Phe--Cyc--PydX--Y                                                                            Ich                                                  ______________________________________                                    

Among these, those of the partial formulae Ica, Icb, Ice and Icf areparticularly preferred.

The preferred compounds of the partial formula Id include those of thepartial formulae Ida to Idm:

    ______________________________________                                        R.sup.1 --Cyc--Cyc--C.tbd.C--PydX--Y                                                                     Ida                                                R.sup.1 --Phe--Phe--C.tbd.C--PydX--Y                                                                     Idb                                                R.sup.1 --Cyc--Phe--C.tbd.C--PydX--Y                                                                     Idc                                                R.sup.1 --Cyc--Phe--CH.sub.2 CH.sub.2 --PydX--Y                                                          Idd                                                R.sup.1 --Cyc--Cyc--CH.sub.2 CH.sub.2 --PydX--Y                                                          Ide                                                R.sup.1 --Phe--Phe--CH.sub.2 CH.sub.2 --PydX--Y                                                          Idf                                                R.sup.1 --Cyc--Cyc--COO--PydX--Y                                                                         Idg                                                R.sup.1 --Phe--Cyc--COO--PydX--Y                                                                         Idh                                                R.sup.1 --Phe--Phe--COO--PydX--Y                                                                         Idi                                                R.sup.1 --Cyc--Phe--COO--PydX--Y                                                                         Idj                                                R.sup.1 --Phe--Phe--CH.sub.2 O--PydX--Y                                                                  Idk                                                R.sup.1 --Cyc--Phe--CH.sub.2 O--PydX--Y                                                                  Idl                                                R.sup.1 --Cyc--Cyc--CH.sub.2 O--PydX--Y                                                                  Idm                                                ______________________________________                                    

Among these, those of the formulae Ida, Idb, Idc, Ide, Idg and Idh areparticularly preferred.

The preferred compounds of the partial formula Ie include those of thepartial formulae Iea to Iem:

    ______________________________________                                        R.sup.1 --Cyc--CH.sub.2 CH.sub.2 --Phe--PydX--Y                                                          Iea                                                R.sup.1 --Phe--CH.sub.2 CH.sub.2 --Phe--PydX--Y                                                          Ieb                                                R.sup.1 --Cyc--C.tbd.C--Phe--PydX--Y                                                                     Iec                                                R.sup.1 --Phe--C.tbd.C--Phe--PydX--Y                                                                     Ied                                                R.sup.1 --Phe--CH.sub.2 O--Phe--PydX--Y                                                                  Iee                                                R.sup.1 --Cyc--COO--Phe--PydX--Y                                                                         Ief                                                R.sup.1 --Cyc--COO--Cyc--PydX--Y                                                                         Ieg                                                R.sup.1 --A.sup.1 --OCO--Phe--PydX--Y                                                                    Ieh                                                R.sup.1 --A.sup.1 --OCH.sub.2 --Phe--PydX--Y                                                             Iei                                                R.sup.1 --A.sup.1 --Z.sup.1 --Pyd--PydX--Y                                                               Iej                                                R.sup.1 --A.sup.1 --Z.sup.1 --Pyr--PyrdX--Y                                                              Iek                                                R.sup.1 --Cyc--C.tbd.C--Cyc--PydX--Y                                                                     Iel                                                R.sup.1 --Cyc--CH.sub.2 CH.sub.2 --Cyc--PydX--Y                                                          Iem                                                ______________________________________                                    

Among these, those of partial formulae Iea, Ieb, Iec, Ied, Ieg and Ielare particularly preferred.

The preferred compounds of the partial formula If include those of thepartial formulae Ifa to Ifh:

    ______________________________________                                        R.sup.1 --A.sup.1 --Z.sup.1 --Phe--C.tbd.C--PydX--Y                                                       Ifa                                               R.sup.1 --A.sup.1 --CH.sub.2 CH.sub.2 --Phe--CH.sub.2 CH.sub.2 --PydX--Y                                  Ifb                                               R.sup.1 --A.sup.1 --Z.sup.1 --Phe--CH.sub.2 CH.sub.2 --PydX--Y                                            Ifc                                               R.sup.1 --A.sup.1 --Z.sup.1 --Cyc--COO--PydX--Y                                                           Ifd                                               R.sup.1 --Cyc--Z.sup.1 --Cyc--C.tbd.C--PydX--Y                                                            Ife                                               R.sup.1 --Cyc--Z.sup.1 --Cyc--CH.sub.2 CH.sub.2 --PydX--Y                                                 Iff                                               R.sup.1 --A.sup.1 --COO--Phe--Z.sup.2 --PydX--Y                                                           Ifg                                               R.sup.1 --A.sup.1 --CH.sub.2 O--Phe--Z.sup.2 PydX--Y                                                      Ifh                                               ______________________________________                                    

The preferred compounds of the formulae Ig to In include those of thepartial formulae Iga to Igo:

    ______________________________________                                        R.sup.1 --A.sup.1 --Cyc--Cyc--PydX--Y                                                                      Iga                                              R.sup.1 --Cyc--Cyc--Phe--PydX--Y                                                                           Igb                                              R.sup.1 --Phe--Phe--Cyc--PydX--Y                                                                           Igc                                              R.sup.1 --A.sup.1 --CH.sub.2 CH.sub.2 --A.sup.1 --Cyc --PydX--Y                                            Igd                                              R.sup.1 --Cyc--COO--A.sup.1 --Phe--PydX--Y                                                                 Ige                                              R.sup.1 --A.sup.1 --A.sup.1 --CH.sub.2 CH.sub.2 --Phe--PydX--Y                                             Igf                                              R.sup.1 --Cyc--Cyc--Z.sup.1 --A.sup.2 --PydX--Y                                                            Igg                                              R.sup.1 --A.sup.1 --Phe--Phe--C.tbd.C--PydX--Y                                                             Igh                                              R.sup.1 --A.sup.1 --Cyc--Phe--C.tbd.C--PydX--Y                                                             Igi                                              R.sup.1 --A.sup.1 --A.sup.1 --A.sup.2 --CH.sub.2 CH.sub.2 --PydX--Y                                        Igj                                              R.sup.1 --A.sup.1 --A.sup.1 --A.sup.2 --COO--PydX--Y                                                       Igk                                              R.sup.1 --Cyc--COO--A.sup.1 --Z.sup.1 --Phe--PydX--Y                                                       Igl                                              R.sup.1 --Phe--C.tbd.C--A.sup.1 --Z.sup.1 --Phe--PydX--Y                                                   Igm                                              R.sup.1 --A.sup.1 --CH.sub.2 CH.sub.2 -- Cyc--Cyc--CH.sub.2 CH.sub.2          --PydX--Y                    Ign                                              R.sup.1 --A.sup.1 --Z.sup.1 --Phe--Phe--Z.sup.2 --PydX--Y                                                  Igo                                              ______________________________________                                    

In the compounds of the formulae above and below Y is F, Cl, --CF₃, --OCF₃ or --OCF₂ H, preferably F or --CF₃. X is H or F, preferably H.However, in case of Y is F or Cl, X preferably is F, too.

In the compounds of the formulae above and below R¹ is preferably alkyl,alkoxy, oxaalkyl, alkanoyloxy or alkenyl and can exhibit astraight-chain or branched structure.

Alkyl or alkoxy preferably are straight-chain and have 2, 3, 4, 5, 6 or7 C atoms. Accordingly they are preferably ethyl, propyl, butyl, pentyl,hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, or heptoxy,also methyl, octyl, nonyl, decyl, undecyl, dodecyl, methoxy, octoxy,nonoxy, decoxy or undecoxy

Oxaalkyl is preferably straight-chain 2-oxapropyl (=methoxymethyl),2-(=ethoxymethyl) or 3-oxybutyl (=2-methoxyethyl), 2-, 3- or4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4- 5- or 6-oxaheptyl, 2-,3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or2-, 3-, 4-, 5-, 6-, 7-, 8-, or 9-oxadecyl.

Alkenyl is preferably straight-chain and has 2 to 10 C atoms. It isaccordingly, in particular, vinyl, prop-1- or prop-2-enyl, but-1-, -2-or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or™5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-,-5- -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -B-enyl ordec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.

Compounds of the formula I containing a branched terminal group canoccasionally be of importance because of an improved solubility in thecustomary liquid crystal base materials, but in particular as chiraldoping substances if they are optically active.

Branched groups of this type as a rule contain not more than one chainbranching. Preferred branched radicals are isopropyl, 2-butyl(=1-methylpropyl), isobutyl (=2-methylpropyl, 2-methylbutyl, isopentyl,(=3-methylbutyl), 2-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl,isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy,2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 2-methylhexoxy,1-methylhexoxy, 1-methylheptoxy (=2-octyloxy), 2-oxa-3-methylbutyl,3-oxa-4-methylhexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxy,6-methyloctanoyloxy, 4-methylheptyloxycarbonyl, 2-methylbutyryloxy,3-methylvaleryloxy, 4-methylhexanoyloxy, 2-methyl-3-oxapentyl and2-methyl-3-oxahexyl.

In the case of compounds with a branched terminal group R¹, formula Iincludes both the optical antipodes and racemates as well as mixturesthereof.

n is preferably 0 or 1. If n is 2, the two groups A¹ and Z¹ may beidentical or different from one another.

Z¹ and Z² are preferably a single bond, a --CH₂ CH₂ --, a --CO--O-- or a--CH₂ CH₂ -group, also --O--CO--, --CH₂ O-- or --OCH₂ --.

A¹ and A² are preferably unsubstituted 1,4-phenylene or trans1,4-cyclohexylene. Compounds wherein A.sup. and/or A² are substituted1,4-phenylene are also preferred. They are then preferably mono- ordisubstituted by fluorine and the 1,4-phenylene group has preferably thefollowing structures: ##STR5##

A¹ and A² also preferably have the meaning of Pyd or Pyr.

the following group of compounds of the formula I is particularlypreferred: ##STR6##

Of The compounds of the formula I and subformula thereof, those in whichat least one of the radicals contained therein has one of the preferredmeanings given are preferred.

The compounds of the formula I are prepared by methods which are knownper se, such as are described in the literature (for example in thestandard works, such as Houben-Weyl, Methoden der Organischen Chemie[Methods of Organic Chemistry, Georg Thieme Verlag, Stuttgart), and inparticular under reaction conditions which are known and suitable forthe reactions mentioned. Variants which are known per se and are notmentioned in more detail here can also be used in this connection.

If desired, the starting materials can also be formed in situ, such thatthey are not isolated from the reaction mixture but are immediatelyreacted further to give the compounds of the formula I.

The most important starting materials for most of the synthesis routesare the following substances: ##STR7##

these key intermediates are preparable by the following routes(LDA=lithiumdiisopropylamide) ##STR8##

The compounds of the formula I thus can be prepared preferably by thefollowing coupling reactions which are known per se: ##STR9##

The compounds of the formula I wherein X denotes --OCF₃ can be obtainedfor example from the compounds of the formula I wherein X denotes Cl orF by nucleophilic substitution with sodium trifluoromethanolate.

The compounds of the formula I wherein X denotes --OCF₂ H can beprepared as described in WO 90/01056, for example, by reacting thehydroxypyridines of the formula I' ##STR10## with chlorodifluoromethane.

The reaction conditions are known to the skilled worker or described inthe literature already mentioned. Other routes are apparent to theskilled worker.

Compounds of the formula I wherein X=Y=F are highly useful as startingmaterials for liquid crystalline compounds with the structural element##STR11##

Compounds having this structural element are obtained by a nucleophilicsubstitution of the terminal F atom by --OR, wherein R is an organicresidue.

In addition to one or more compounds of the formula I the liquid crystalmedia according to the invention preferably contain 2-40 components andin particular 4-30 components. Liquid crystal media being composed ofone or more compounds of formula I and 7-25 other components areespecially preferred.

These additional components are preferably chosen from the nematic ornematogenic (monotropic or isotropic) substances; in particular from theclasses of azoxybenzenes, benzylideneanilines, biphenyls, terphenyls,phenyl or cyclohexyl benzoates, phenyl or cyclohexylcyclohexanecarboxylates, phenyl or cyclohexyl cyclohexylbenzoates,phenyl or cyclohexyl cyclohexylcyclohexanecarboxylates,cyclohexylphenylbenzoates, cyclohexylphenyl cyclohexanecarbox-ylates,cyclohexylphenyl cyclohexylcyclohexanecarboxylates, phenylcyclohexanes,cyclohexylbiphenyls, phenylcyclohexylcyclohexanes,cyclohexylcyclohexanes, cyclohexylcyclohexenes,cyclohexylcyclohex-Ylcyclohexene, 1,4-bis-cyclohexylbenzenes,4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl-or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- orcyclo™hexyl-1,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexylethanes,1-phenyl-2-cyclohexylethanes,1-cyclohexyl-2-(4-phenyl-cyclohex-yl)-ethanes,1-cyclohexyl-2-biphenylethanes, 1-phenyl-2-cyclohex-yl-phenylethanes,optionally halogenated stilbenes, benzyl phenyl ethers, tolanes andsubstituted cinnamic acids.

The 1,4-phenylene groups of these compounds may be fluorinated.

The most important compounds which are possible constituents of liquidcrystal media according to the invention can be characterized by theformalae 1, 2, 3, 4 and 5:

    R'--L--U--R"                                               1

    R'--L--COO--U--R"                                          2

    R'--L--OOC--U--R"                                          3

    R'--L--CH.sub.2 CH.sub.2 --U--R"                           4

    R'--L--C.tbd.C--U--R"                                      5

In the formulae 1, 2, 3, 4 and 5 L and U may be equal or different fromeach other. L and U independently from each other denote a bivalentresidue selected from the group consisting of -Phe-, -Cyc-, -Phe-Phe-,-Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe-, -G-Cyc- and their mirrorimages; in this compilation of residues Phe denotes unsubstituted orfluorinated 1,4-phenylene, Cyc trans- 1,4-cyclohexylene or1,4-cyclohexenylene, Pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio1,3-dioxane-2,5-diyl and G 2-(trans-1,4-cyclohexyl)-ethyl,pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.

One of the residues L and U is preferably Cyc, Phe or Pyr. U preferablydenotes Cyc, Phe or Phe-Cyc. The liquid crystal media according to theinvention preferably contain one or more components selected from thecompounds of formulae I, 2, 3, 4 and 5 with L and U meaning Cyc, Phe andPyr, said liquid crystal media further containing at the same time oneore more components selected from the compounds of formulae 1, 2, 3, 4and 5 with one of the residues L and U denoting Cyc, Phe and Pyr and theother residue being selected from the group consisting of -Phe-Phe-,-Phe-Cyc-, -Cyc-Cyc-, -G-Cyc-, said liquid crystal media containing inaddition to this optionally one or more components selected from thecompounds of formulae I, 2, 3, 4 and 5 with L and U being selected fromthe group consisting of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc.

In a preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5(subgroup 1) R' and R" are independently from each other alkyl, alkenyl,alkoxy, alkenoxy with up to 8 carbon atoms. R' and R" differ from oneanother in most of these compounds, one of the residues usually beingalkyl or alkenyl. In another preferred subgroup of the compounds offormulae 1, 2, 3, 4 and 5 (subgroup 2) R" denotes --CN, --CF₃, --F, --Clor --NCS while R' has the meaning indicated in subgroup 1 and ispreferably alkyl or alkenyl. Other variants of the envisagedsubstituents in the compounds of formulae 1, 2, 3, 4 and 5 are alsocustomary. Many such substances are commercially available. All thesesubstances are obtainable by methods which are known from the literatureor by analogous methods.

The liquid crystal media according to the invention preferably containin addition to components selected from subgroup 1 also components ofsubgroup 2, the percentage of these components being as follows:

subgroup 1: 20 to 90%, in particular 30 to 90%

subgroup 2: 10 to 50%, in particular 10 to 50%

In these liquid crystal media the percentages of the compounds accordingto the invention and the compounds of subgroup 1 and 2 may add up togive 100%.

The media according to the invention preferably contain 1 to 40%, inparticular 5 to 30% of the compounds according to the invention. Mediacontaining more than 40%, in particular 45 to 90% of the compoundsaccording to the invention are further preferred. The media containpreferably 3, 4 or 5 compounds according to the invention.

The media according to the invention are prepared in a manner which iscustomary per se. As a rule, the components are dissolved in oneanother, advantageously at elevated temperature. The liquid crystalmedia according to the invention can be modified by suitable additivesso that they can be used in all the types of liquid crystal displaydevices. Such additives are known to the expert and are described indetail in the literature (H. Kelker/R. Hatz, Handbook of LiquidCrystals, Verlag Chemie, Weinheim, 1980). For example, it is possible toadd pleochroic dyestuffs to prepare colored guest-host systems orsubstances for modifying the dielectric anisotropy, the viscosity and/orthe orientation of the nematic phases.

The following examples are to be construed as merely illustrative andnot limitative. m.p.=melting point, c.p.=clearing point. In theforegoing and in the following all parts and percentages are by weightand the temperatures are set forth in degrees Celsius. "Customarywork-up" means that water is added, the mixture is extracted withmethylene chloride, the organic phase is separated off, dried andevaporated, and the product is purified by crystallization and/orchromatography.

Further are:

C: crystalline-solid state, S: smectic phase (the index denoting thetype of smectic phase), N: nematic phase, Ch: cholesteric phase, I:isotropic phase. The number being embraced by 2 of these symbols denotesthe temperature of phase change.

EXAMPLES Example 1

a) 48.5 mM of magnesium in 8 ml of THF is slowly added under drynitrogen to a mixture of 44.1 mM of 2-fluoro-5-bromopyridine (obtainableby reacting 2-chloro-5-nitropyridine with anhydrous KF in DMF at 120° ,hydrogenation of the nitro-group and transferring the NH₂ -group withNaNO₂ via the diazonium salt and with HBr into the bromo-derivative) in50 ml of THF. The Grignard reagent is refluxed for a further hour,cooled in ice and 53.4 mM of trimethylborate is added. After stirringovernight the borate ester is hydrolysed with dilute HCl, the productextracted into ether, dried and the solvent removed.

b) 35 mM of 4-(trans-4-pentylcyclohexyl)-bromobenzene, 38.5 mM of2-fluoro-pyridine-5-bromic acid and Pd(PPh₃)₄ (4×10⁻⁴) are refluxedovernight under nitrogen, in a mixture of toluene (45 ml), aqueous Na₂CO₃ (20 ml) and 15 ml of IMS. Customary work-up gives2-fluoro-5-[4-(trans-4-pentylcyclohexyl)phenyl-pyridine.

The following compounds are obtained analogously:

2-fluoro-5-[4-(trans-4-ethylcyclohexyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-propylcyclohexyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-butylcyclohexyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-hexylcyclohexyl)phenyl]-pyridine

2-fluoro-5-4-(trans-4-heptylcyclohexyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-ethylcyclohexyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-propylcyclohexyl)phenyl]-pyridine, K 142 N 191.3I visc 80 cSt

2-chloro-5-[4-(trans-4-butylcyclohexyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-pentylcyclohexyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-hexylcyclohex-yl)phenyl-pyridine

2-chloro-5-[4-(trans-4-heptylcyclohexyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-ethylcyclohexyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-propylcyclohexyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-butylcyclohexyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-pentylcyclohexyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-hexylcyclohexyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-heptylcyclohexyl)phenyl-pyridine

2-fluoro-5-[4-(trans-4-ethylcyclohexylethyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-propylcyclohexylethyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-butylcyclohexylethyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-pentylcyclohexylethyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-hexylcyclohexylethyl)phenyl-pyridine

2-fluoro-5-[4-(trans-4-heptylcyclohexylethyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-ethylcyclohexylethyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-propylcyclohexylethyl)phenyl]-pyridine, K 142 N159 I visc 83 cSt

2-chloro-5-[4-(trans-4-butylcyclohexylethyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-pentylcyclohexylethyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-hexylcyclohexylethyl)phenyl]-pyridine

2-chloro-5-[4-(trans-4-heptylcyclohexylethyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-ethylcyclohexylethyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-propylcyclohexylethyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-butylcyclohexylethyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-pentylcyclohexylethyl)

2-trifluoromethyl-5-[4-(trans-4-hexylcyclohexylethyl)phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-heptylcyclohexylethyl)phenyl]-pyridine

2-fluoro-5-[4-(trans-4-ethylcyclohexyl)-2-fluorophenyl]-pyridine

2-fluoro-5-[4-(trans-4-propylcyclohexyl)-2-fluorophenyl]-pyridine

2-fluoro-5-[4-(trans-4-butylcyclohexyl)-2-fluorophenyl]-pyridine

2-fluoro-5-[4-(trans-4-pentylcyclohexyl)-2-fluorophenyl]-pyridine

2-fluoro-5-[4-(trans-4-hexylcyclohexyl)-2-fluorophenyl]-pyridine

2-fluoro-5-[4-(trans-4-heptylcyclohexyl)-2-fluorophenyl]-pyridine

2-fluoro-5-[4-(trans-4-octylcyclohexyl)-2-fluorophenyl]-pyridine

2-chloro-5-[4-(trans-4-ethylcyclohexyl)-3-fluorophenyl]-pyridine

2-chloro-5-[4-(trans-4-propylcyclohexyl)-3-fluorophenyl]-pyridine

2-chloro-5-4-(trans-4-butylcyclohexyl)-3-fluorophenyl]-pyridine

2-chloro-5-[4-(trans-4-pentylcyclohexyl)-3-fluorophenyl]-pyridine

2-chloro-5-[4-(trans-4-hexylcyclohexyl)-3-fluorophenyl]-pyridine

2-chloro-5-[4-(trans-4-heptylcyclohexyl)-3-fluorophenyl]-pyridine

2-trifluoromethyl-5-4-(trans-4-ethylcyclohexylethyl)-2-fluorophenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-propylcyclohexylethyl)-2-fluorophenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-butylcyclohexylethyl)-2-fluorophenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-pentylcyclohexylethyl)-2-fluorophenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-hexylcyclohexyl)-2-fluoro-phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-heptylcyclohexyl)-2-fluoro-phenyl]-pyridine

2-trifluoromethyl-5-[4-(trans-4-octylcyclohexyl)-2-fluoro-phenyl]-pyridine

2-fluoro-5-(4-ethylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-propylbiphenyl-4'-yl)-pyridine

2-fluoro™5-(4-butylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-pentylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-hexylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-heptylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(2-fluoro-4-ethylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(2-fluoro-4-propylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(2-fluoro-4-butylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(2-fluoro-4-pentylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(2-fluoro-4-hexylbiphenyl-4'-yl)-pyridine

2-fluoro-5-(2-fluoro-4-heptylbiphenyl-4'-yl)-pyridine

2-chloro-5-(2'-fluoro-4-ethylbiphenyl-4'-yl)-pyridine

2-chloro-5-(2'-fluoro-4-propylbiphenyl-4'-yl)-pyridine

2-chloro-5-(2'-fluoro-4-butylbiphenyl-4'-yl)-pyridine

2-chloro-5-(2'-fluoro-4-pentylbiphenyl-4'-yl)-pyridine

2-chloro-5-(2'-fluoro-4-hexylbiphenyl-4'-yl)-pyridine

2-chloro-5-(2'-fluoro-4-heptylbiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(3-fluoro-4-ethylbiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(3-fluoro-4-propylbiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(3-fluoro-4-butylbiphenyl-4'-yl)pyridine

2-trifluoromethyl-5-(3-fluoro-4-pentylbiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(3-fluoro-4-hexylbiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(3-fluoro-4-heptylbiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(3-fluoro-4-methylbiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(4-ethoxybiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(4-propoxybiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(4-methoxybiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(4-butoxybiphenyl-4'-yl)-pyridine

2-trifluoromethyl™5-(4-pentyloxybiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(4-hexyloxybiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(4-heptyloxybiphenyl-4'-yl)-pyridine

2-trifluoromethyl-5-(4-octyloxybiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-ethoxybiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-propoxybiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-butoxybiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-pentyloxybiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-heptyloxybiphenyl-4'-yl)-pyridine

2-fluoro-5-(4-ethylphenyl)-pyridine

2-fluoro-5-(4-propylphenyl)-pyridine

2-fluoro-5-(4-butylphenyl)-pyridine

2-fluoro-5-(4-pentylphenyl)-pyridine

2-fluoro-5-(4-hexylphenyl)-pyridine

2-fluoro-5-(4-heptylphenyl)-pyridine

2-fluoro-5-(4-ethoxyphenyl)-pyridine

2-fluoro-5-(4-butoxyphenyl)-pyridine

2-fluoro-5-(4-propoxyphenyl)-pyridine

2-fluoro-5-(4-pentyloxyphenyl)-pyridine

2-chloro-5-(4-ethylphenyl)-pyridine

2-chloro-5-(4-propylphenyl)-pyridine

2-chloro-5-(4-butylphenyl)-pyridine

2-chloro-5-(4-pentylphenyl)-pyridine

2-chloro-5-(4-hexylphenyl)-pyridine

2-chloro-5-(4-heptylphenyl)-pyridine

2-chloro-5-(4-ethoxyphenyl)-pyridine

2-chloro-5-(4-propoxyphenyl)-pyridine

2-chloro-5-(4-pentyloxyphenyl)-pyridine

2-chloro-5-(4-octyloxyphenyl)-pyridine

2-fluoro-5-(2-fluoro-4-ethylphenyl)-pyridine

2-fluoro-5-(2-fluoro-4-propylphenyl)-pyridine

2-fluoro-5-(2-fluoro-4butylphenyl)-pyridine

2-fluoro-5-(2-fluoro-4-pentylphenyl)-pyridine

2-fluoro-5-(2-fluoro-4-hexylphenyl)-pyridine

2-fluoro-5-(2-fluoro-4-heptylphenyl)-pyridine

2-trifluoromethyl-5-(4-ethoxyphenyl)-pyridine

2-trifluoromethyl-5-(4-propoxyphenyl)-pyridine

2-trifluoromethyl-5-(4-butoxyphenyl)-pyridine

2-trifluoromethyl-5-(4-ethylphenyl)-pyridine

2-trifluoromethyl-5-(4-propylphenyl)-pyridine

2-trifluoromethyl-5-(4-butylphenyl)-pyridine

2-trifluoromethyl-5-(4-pentylphenyl)-pyridine

2-trifluoromethyl-5-(4-hexylphenyl)-pyridine

2-trifluoromethyl-5-(4-heptylphenyl)-pyridine

2-trifluoromethoxy-5-(4-ethylphenyl)-pyridine

2-trifluoromethoxy-5-(4-propylphenyl)-pyridine

2-trifluoromethoxy-5-(4-butylphenyl)-pyridine

2-trifluoromethoxy-5-(4-pentylphenyl)-pyridine

2-difluoromethoxy-5-(4-ethylphenyl)-pyridine

2-difluoromethoxy-5-(4-propylphenyl)-pyridine

2-difluoromethoxy-5-(4-butylphenyl)-pyridine

2-difluoromethoxy-5-(4-pentylphenyl)-pyridine

2-difluoromethoxy-5-(4-hexylphenyl)-pyridine

2-difluoromethoxy-5-(4-ethoxyphenyl)-pyridine

EXAMPLE 2

To a mixture of 0.1 M of 2,6-difluoro-3-hydroxypyridine (obtainable byreaction of 2,6-difluoro-pyridine-3-boronic acid with H₂ O₂ in ether),0.1 M of trans-4-pentylcyclohexane carboxylic acid, 0.1 Mdimethylaminopyridine (DMAP) and 200 ml of C a solution of 0.11 M ofdicyclohexylcarbodiimide (DCC) in C is added at 15°-20° C.

After stirring for 5 hours at room temperature and customary work-up,2,6-difluoropyridine-3-yl trans-4-pentylcyclohexanecarboxylate isobtained.

The following components are obtained analogously:

2,6-difluoropyridine-3-yl trans-4-ethylcyclohexanecarboxylate

2,6-difluoropyridine-3-yl trans-4-propylcyclohexanecarboxylate

2,6-difluoropyridine-3-yl trans-4-butylcyclohexanecarboxylate

2,6-difluoropyridine-3-yltrans-4-(trans-4-ethylcyclohexyl)-cyclohexanecarboxylate

2,6-difluoropyridine-3-yltrans-4-(trans-4-propylcyclohexyl)-cyclohexanecarboxylate

2,6-difluoropyridine-3-yltrans-4-(trans-4-butylcyclohexyl)-cyclohexanecarboxylate

2,6-difluoropyridine-3-yltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanecarboxylate

2-fluoropyridine-5-yltrans-4-(trans-4-ethylcyclohexyl)cyclohexanecarboxylate

2-fluoropyridine-5-yltrans-4-(trans-4-propylcyclohexyl)cyclohexanecarboxylate

2-fluoropyridine-5-yltrans-4-(trans-4-butylcyclohexyl)cyclohexanecarboxylate

2-fluoropyridine-5-yltrans-4-(trans-4-pentylcyclohexyl)cyclohexanecarboxylate

2-fluoropyridine-5-yltrans-4-(trans-4-heptylcyclohexyl)cyclohexanecarboxylate

2-chloropyridine-5-yltrans-4-(trans-4-ethylcyclohexyl)cyclohexanecarboxylate

2-chloropyridine-5-yltrans-4-(trans-4-propylcyclohexyl)cyclohexanecarboxylate

2-chloropyridine-5-yltrans-4-(trans-4-butylcyclohexyl)cyclohexanecarboxylate

2-chloropyridine-5-yltrans-4-(trans-4-pentylcyclohexyl)cyclohexanecarboxylate

2-chloropyridine-5-yltrans-4-(trans-4-octylcyclohexyl)cyclohexanecarboxylate

2-trifluoromethylpyridine-5-yl trans-4-ethylcyclohexanecarboxylate

2-trifluoromethylpyridine-5-yl trans-4-propylcyclohexanecarboxylate

2-trifluoromethylpyridine-5-yltrans-4-butylcyclohexanecarboxylatecarboxylate

2-trifluoromethylpyridine-5-yl trans-4-pentylcyclohexanecarboxylate

2-trifluoromethylpyridine-5-yl trans-4-hexylcyclohexanecarboxylate

2-trifluoromethoxypyridine-5-yl trans-4-propylcyclohexanecarboxylate

2-trifluoromethoxypyridine-5-yl trans-4-butylcyclohexanecarboxylate

2-trifluoromethoxypyridine-5-yl trans-4-pentylcyclohexanecarboxylate

2-trifluoromethoxypyridine-5-yl trans-4-hexylcyclohexanecarboxylate

2-difluoromethoxypyridine-5-yl trans-4-propylcyclohexanecarboxylate

2-difluoromethoxypyridine-5-yl trans-4-butylcyclohexanecarboxylate

2-difluoromethoxypyridine-5-yl trans-4-pentylcyclohexanecarboxylate

2-difluoromethoxypyridine-5-yl trans-4-hexylcyclohexanecarboxylate

2-difluoromethoxypyridine-5-yl trans-4-heptylcyclohexanecarboxylate

2-fluoro-6-chloropyridine-3-yl trans-4-ethylcyclohexanecarboxylate

2-fluoro-6-chloropyridine-3-yl trans-4-propylcyclohexanecarboxylate

2-fluoro-6-chloropyridine-3-yl trans-4-butylcyclohexanecarboxylate

2-fluoro-6-chloropyridine-3-yl trans-4-pentylcyclohexanecarboxylate

2,6-difluoropyridine-3-yl 4-ethylbenzoate

2,6-difluoropyridine-3-yl 4-propylbenzoate

2,6-difluoropyridine-3-yl 4-butylbenzoate

2,6-difluoropyridine-3-yl 4-pentylbenzoate

2,6-difluoropyridine-3-yl 4-ethoxybenzoate

2,6-difluoropyridine-3-yl 4-propoxybenzoate

2,6-difluoropyridine-3-yl 4-butoxybenzoate

2,6-difluoropyridine-3-yl 4-pentyloxybenzoate

2,6-difluoropyridine-3-yl 4-hexyloxybenzoate

2,6-difluoropyridine-3-yl 4-heptyloxybenzoate

2,6-difluoropyridine-3-yl 4-octyloxybenzoate

2-fluoropyridine-5-yl 4-ethylbenzoate

2-fluoropyridine-5-yl 4-propylbenzoate

2-fluoropyridine-5-yl 4-butylbenzoate

2-fluoropyridine-5-yl 4-pentylbenzoate

2-fluoropyridine-5-yl 4-ethoxybenzoate

2-fluoropyridine-5-yl 4-propoxybenzoate

2-fluoropyridine-5-yl 4-butoxybenzoate

2-fluoropyridine-5-yl 4-pentyloxybenzoate

2-fluoropyridine-5-yl 4-hexyloxybenzoate

2-fluoropyridine-5-yl 4-heptyloxybenzoate

2-fluoropyridine-5-yl 4-octyloxybenzoate

2-trifluoromethylpyridine-5-yl 4-ethylbenzoate

2-trifluoromethylpyridine-5-yl 4-propylbenzoate

2-trifluoromethylpyridine-5-yl 4-butylbenzoate

2-trifluoromethylpyridine-5-yl 4-pentylbenzoate

2-trifluoromethoxypyridine-5-yl 4-ethoxybenzoate

2-trifluoromethoxypyridine-5-yl 4-propoxybenzoate

2-trifluoromethoxypyridine-5-yl 4-butoxybenzoate

2-trifluoromethoxypyridine-5-yl 4-penthyloxybenzoate

2-trifluoromethoxypyridine-5-yl- 4-hexyloxybenzoate

2-trifluoromethoxypyridine-5-yl 4-heptyloxybenzoate

2-trifluoromethoxypyridine-5-yl 4-octyloxybenzoate

2-difluoromethoxypyridine-5-yl 4-ethoxybenzoate

2-difluoromethoxypyridine-5-yl 4-propoxybenzoate

2-difluoromethoxypyridine-5-yl 4-butoxybenzoate

2-difluoromethoxypyridine-5-yl 4-pentoxybenzoate

2-difluoromethoxypyridine-5-yl 4-hexoxybenzoate

2-difluoromethoxypyridine-5-yl 4-heptoxybenzoate

2-fluoropyridine-5-yl trans-4-ethylcyclohexanecarboxylate

2-fluoropyridine-5-yl trans-4-propylcyclohexanecarboxylate

2-fluoropyridine-5-yl trans-4-butylcyclohexanecarboxylate

2-fluoropyridine-5-yl trans-4-pentylcyclohexanecarboxylate

2-trifluoromethylpyridine-5-yltrans-4-(trans-4-ethylcyclohexyl)-cyclohexanecarboxylate

2-trifluoromethylpyridine-5-yltrans-4-(trans-4-propylcyclohexyl)-cyclohexanecarboxylate

2-trifluoromethylpyridine-5-yltrans-4-(trans-4-butylcyclohexyl)-cyclohexanecarboxylate

2-trifluoromethylpyridine-5-yltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanecarboxylate

2-chloropyridine-5-yl 4-(4-ethylphenyl)benzoate

2-chloropyridine-5-yl 4-(4-propylphenyl)benzoate

2-chloropyridine-5-yl 4-(4-butylphenyl)benzoate

2-chloropyridine-5-yl 4-(4-pentylphenyl)benzoate

2-chloropyridine-5-yl 4-(4-octylphenyl)benzoate

6-chloro-2-fluoropyridine-3-yl 4-(4-ethylphenyl)benzoate

6-chloro-2-fluoropyridine-3-yl 4-(4-propylphenyl)benzoate

6-chloro-2-fluoropyridine-3-yl 4-(4-butylphenyl)benzoate

6-chloro-2-fluoropyridine-3-yl 4-(4-pentylphenyl)benzoate

6-chloro-2-fluoropyridine-3-yl 4-(4-heptylphenyl)benzoate

2,6-difluoropyridine-3-yl 4-(trans-4-ethylcyclohexyl)benzoate

2,6-difluoropyridine-3-yl 4-(trans-4-propylcyclohexyl)benzoate

2,6-difluoropyridine-3-yl 4-(trans-4-butylcyclohexyl)benzoate

2,6-difluoropyridine-3-yl 4-(trans-4-pentylcyclohexyl)benzoate

2,6-difluoropyridine-3-yl trans-4-(4-ethylphenyl)cyclohexanecarboxylate

2,6-difluoropyridine-3-yl trans-4-(4-propylphenyl)cyclohexanecarboxylate

2,6-difluoropyridine-3-yl trans-4-(4-butylphenyl)cyclohexanecarboxylate

2,6-difluoropyridine-3-yl trans-4-(4-pentylphenyl)cyclohexanecarboxylate

Example 3

a) 0,6 M of n-butyllithium are added at -10° to 0,6 M of diisopropylaminin 600 ml THF. The mixture is cooled to -70°, 0,6 M of2,6-difluoropyridin are added and after stirring for 15 minutes 0,6 M oftrimethylborate are added at the same temperature. The mixture isallowed to warm up to -30°. Then the borate ester is hydrolysed withdilute HCl, the product extracted with ether, washed, dried and thesolvent removed. Thus, 2,6-difluoro-pyridine-3-boronic acid is obtained.

b) A mixture of 0,05 M of 4-(trans-4-pentylcyclohexyl)bromobenzene, 0,06M of 2,6-difluoropyridine-3-boronic acid, 1,25 g of Pd(PPh₃)₄, 100 ml oftoluene, 40 ml of ethanol and 50 ml of 2 M Na₂ CO₃ -solution is heatedat 60 ° C under stirring for 2 hours. Customary work-up andrecrystallisation from ethanol gives2,6-difluoro-3-[4-(trans-4-pentylcyclohexyl)phenyl]-pyridine with C 58°N 107° I.

The following compounds are obtained analogously:

2,6-difluoro-3-[4-(trans-4-ethylcyclohexyl)phenyl]-pyridine

2,6-difluoro-3-[4-(trans-4-propylcyclohexyl)phenyl]-pyridine

2,6-difluoro-3-[4-(trans-4-butylcyclohexyl)phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-ethylcyclohexyl)phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-propylcyclohexyl)phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-butylcyclohexyl)phenyl-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-pentylcyclohexyl)phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-hexylcyclohexyl)phenyl]-pyridine

2,6-difluroro-3-[4-(trans-4-ethylcyclohexylethyl)phenyl]-pyridine

2,6-difluroro-3-[4-(trans-4-propylcyclohexylethyl)phenyl-pyridine

2,6-difluroro-3-[4-(trans-4-butylcyclohexylethyl)phenyl-pyridine

2,6-difluroro-3-4-(trans-4-pentylcyclohexylethyl)phenyl]-pyridine

2,6-difluroro-3-[4-(trans-4-octylcyclohexylethyl)phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-ethylcyclohexylethyl)-phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-propylcyclohexylethyl)-phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-butylcyclohexylethyl)phenyl]-pyridine

6-chloro-2-fluoro-3-[4-(trans-4-pentylcyclohexylethyl)phenyl]-pyridine

2,6-difluoro-3-[4-(trans-4-ethylcyclohexyl)-2-fluorophenyl]-pyridine

2,6-difluoro-3-[4-(trans-4-propylcyclohexyl)-2-fluorophenyl]-pyridine

2,6-difluoro-3-4-(trans-4-butylcyclohexyl)-2-fluorophenyl]-pyridine

2,6-difluoro-3-4-(trans-4-pentylcyclohexyl)-2-fluorophenyl]-pyridine

2,6-difluoro-3-[4-(trans-4-heptylcyclohexyl)-2-fluorophenyl]-pyridine

2,6-difluoro-3-(4-ethylbiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-propylbiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-butylbiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-pentylbiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-ethoxybiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-propoxybiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-butoxybiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-pentyloxybiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-hexyloxybiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-heptyloxybiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-octyloxybiphenyl-4'-yl)-pyridine

2,6-difluoro-3-(4-ethylphenyl)-pyridine

2,6-difluoro-3-(4-propylphenyl)-pyridine

2,6-difluoro-3-(4-butylphenyl)-pyridine

2,6-difluoro-3-(4-pentylphenyl)-pyridine

6-chloro-2-fluoro-3-(4-ethylphenyl)-pyridine

6-chloro-2-fluoro-3-(4-propylphenyl)-pyridine

6-chloro-2-fluoro-3-(4-butylphenyl)-pyridine

6-chloro-2-fluoro-3-(4-pentylphenyl)-pyridine

6-chloro-2-fluoro-3-(4-hexylphenyl)-pyridine

2,6-difluoro-3-(4-ethoxyphenyl)-pyridine

2,6-difluoro-3-(4-propoxyphenyl)-pyridine

2,6-difluoro-3-(4-butoxyphenyl)-pyridine

2,6-difluoro-3-(4-pentyloxyphenyl)-pyridine

2,6-difluoro-3-(4-octyloxyphenyl)-pyridine

Example 4

0,2 mM of Pd(Ph₃ P)₂ Cl₂ and 0,1 mM of CuJ are added to a mixture of0,01 M of 3-bromo-2,6-difluoropyridine (preparation:2,6-difluoropyridine is reacted with lithiumdiisopropylamide (LDA) asdescribed in example 3a, then Br₂ is added at -60° to -70°. The mixtureis allowed to warm up to room temperature and worked up, the product ispurified by distillation), 0,01 M of 4-pentylphenylacetylene and 200 mlof triethylamine. The mixture is stirred for 8 hours at roomtemperature; after customary work-up and purification by crystallizationand chromatography1-(4-pentylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene is obtained.

The following compounds are obtained analogously:

1-(4-ethylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-propylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-butylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-hexylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-ethoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-butoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-methoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-propoxyphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-pentyloxyphenyl)-2-(2,6-difluoropyridine-3-yl)-acetylene

1-(4-ethylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

1-(4-propylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

1-(4-butylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

1-(4-pentylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

1-(4-ethylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-propylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-butylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-pentylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-ethoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-propoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-butoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-(4-pentyloxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)acetylene

1-[4-(trans-4-ethylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)acetylen

1-[4-(trans-4-propylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[4-(trans-4-butylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[4-(trans-4-pentylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-ethylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-propylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-butylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-pentylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-hexylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-(trans-4-ethylcyclohexyl)-2-(2,6-difluoropyridine3-yl)acetylene

1-(trans-4-propylcyclohexyl)-2-(2,6-difluoropyridine3-yl)acetylene

1-(trans-4-butylcyclohexyl)-2-(2,6-difluoropyridine3-yl)acetylene

1-(trans-4-pentylcyclohexyl)-2-(2,6-difluoropyridine3-yl)acetylene

1-trans-4-(4-ethoxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-propoxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-butoxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-pentyloxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[trans-4-(4-octyloxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)acetylene

1-[4-(trans-4-ethylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

1-[4-(trans-4-propylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

1-[4-(trans-4-butylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

1-[4-(trans-4-pentylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)acetylene

Example 5

Hydrogenation of1-(4-pentylphenyl)-2-(2,6-difluoropyridine-3-yl)acetylene yields aftercustomary work-up1-(4-pentylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane.

The following compounds are obtained analogously:

1-(4-ethylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-propylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-butylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-hexylphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-ethoxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-butoxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-methoxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-propoxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-pentyloxyphenyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-ethylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane

1-(4-propylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane

1-(4-butylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane

1-(4-pentylphenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane

1-(4-ethylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-propylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-butylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-pentylbiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-ethoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl )ethane

1-(4-propoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-butoxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(4-pentyloxybiphenyl-4'-yl)-2-(2,6-difluoropyridine-3-yl)ethane

1-[4-(trans-4-ethylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[4-(trans-4-propylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[4-(trans-4-butylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[4-(trans-4-pentylcyclohexyl)phenyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-trans-4-(4-ethylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-propylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-butylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-pentylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-trans-4-(4-hexylphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-(trans-4-ethylcyclohexyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(trans-4-propylcyclohexyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(trans-4-butylcyclohexyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-(trans-4-pentylcyclohexyl)-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-ethoxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-propoxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-butoxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-pentyloxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[trans-4-(4-octyloxyphenyl)cyclohexyl]-2-(2,6-difluoropyridine-3-yl)ethane

1-[4-(trans-4-ethylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane

1-4-(trans-4-propylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)-ethane

1-4-(trans-4-butylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane

1-[4-(trans-4-pentylcyclohexyl)phenyl)-2-(6-chloro-2-fluoropyridine-3-yl)ethane

Example 6

Analogously to Example 41-(4-pentylphenyl)-2-(2-fluoropyridine-5-yl)acetylene is obtained byreacting 2-fluoro5-bromopyridine (preparation described in example 1a)with 4-pentylphenylacetylene.

The following compounds are obtained analogously:

1-(4-ethylphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-propylphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-butylphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-heptylphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-ethoxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-propoxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-butoxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-pentyloxyphenyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-ethylphenyl)-2-(2-chloropyridin-5-yl)acetylene

1-(4-propylphenyl)-2-(2-chloropyridin-5-yl)acetylene

1-(4-butylphenyl)-2-(2-chloropyridin-5-yl)acetylene

1-(4-pentylphenyl)-2-(2-chloropyridin-5-yl)acetylene

1-(4-ethoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-(4-propoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-(4-butoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-(4-pentyloxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1(4-ethoxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)acetylene

1-(4-propoxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)acetylene

1-(4-butoxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)acetylene

1-(4-pentyloxyphenyl)-2-(2-trifluormethoxypyridine-5-yl)acetylene

1-(4-propyloxyphenyl)-2-(2-trifluormethoxpyridine-5-yl)acetylene

1-(4-ethoxyphenyl)-2-(2-chloropyridine-5-yl)acetylene

1-(4-propoxyphenyl)-2-(2-chloropyridine-5-yl)acetylene

1-(4-butoxyphenyl)-2-(2-chloropyridine-5-yl)acetylene

1-(4-pentyloxyphenyl)-2-(2-chloropyridine-5-yl)acetylene

1-(4-ethylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-propylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-butylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-pentylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)acetylene

1-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-(4-propylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-(4-pentylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)acetylene

1-(4-propylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)acetylene

1-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)acetylene

1(4-pentylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)acetylene

1-(4-hexylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)acetylene

1-[4-(trans-4-ethylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]acetylene

1-[4-(trans-4-propylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]acetylene

1-[4-(trans-4-butylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]acetylene

1-[4-(trans-4-pentylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]acetylene

1-4-(trans-4-octylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]acetylene

1-trans-4-(4-ethylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)acetylene

1-[trans-4-(4-propylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)acetylene

1-[trans-4-(4-butylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)acetylene

1-[trans-4-(4-pentylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)acetylene

1-[trans-4-(4-ethoxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

1-[trans-4-(4-propoxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

1-[trans-4-(4-butoxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

1-[trans-4-(4-pentyloxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

1-(trans-4-ethylcyclohexyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(trans-4-propylcyclohexyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(trans-4-butylcyclohexyl)-2-(2-fluoropyridine-5-yl)acetylene

1-(trans-4-pentylcyclohexyl)-2-(2-fluoropyridine-5-yl)acetylene

1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)acetylene

1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

1-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)acetylene

Example 7

Hydrogenation of 1-(4-pentylphenyl)-2-(2-fluoropyridine5-yl)acetyleneyields after customary work-up1-(4-pentylphenyl)-2-(2-fluoropyridine-5-yl)ethane

The following compounds are prepared analogously:

1-(4-ethylphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-propylphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-butylphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-heptylphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-ethoxyphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-propoxyphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-butoxyphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-pentyloxyphenyl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-ethylphenyl)-2-(2-chloropyridin-5-yl)ethane

1-(4-propylphenyl)-2-(2-chloropyridin-5-yl)ethane

1-(4-butylphenyl)-2-(2-chloropyridin-5-yl)ethane

1-(4-pentylphenyl)-2-(2-chloropyridin-5-yl)ethane

1-(4-ethoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)ethane

1-(4-propoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)ethane

1-(4-butoxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)ethane

1-(4-pentyloxyphenyl)-2-(2-trifluoromethylpyridine-5-yl)ethane

1-(4-ethoxyphenyl)-2-(2-chloropyridine-5-yl)ethane

1-(4-propoxyphenyl)-2-(2-chloropyridine-5-yl)ethane

1-(4-butoxyphenyl)-2-(2-chloropyridine-5-yl)ethane

1-(4-pentyloxyphenyl)-2-(2-chloropyridine-5-yl)ethane

1-(4-ethylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-propylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-butylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-pentylbiphenyl-4'-yl)-2-(2-fluoropyridine-5-yl)ethane

1-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5yl)ethane

1-(4-propylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5-yl)ethane

1-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5-yl)ethane

1-(4-pentylbiphenyl-4'-yl)-2-(2-trifluoromethylpyridine-5-yl)ethane

1-(4-ethylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)ethane

1-(4-propylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)ethane

1-(4-butylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)ethane

1-(4-pentylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)ethane

1-(4-hexylbiphenyl-4'-yl)-2-(2-trifluoromethoxypyridine-5-yl)ethane

1-[4-(trans-4-ethylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]ethane

1-[4-(trans-4-propylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]ethane

1-[4-(trans-4-butylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl]ethane

1-[4-(trans-4-pentylcyclohexyl)phenyl]-2-2-fluoropyridine-5-yl]ethane

1-[4-(trans-4-octylcyclohexyl)phenyl]-2-[2-fluoropyridine-5-yl)ethane

1-[trans-4-(4-ethylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)ethane

1-[trans-4-(4-propylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)ethane

1-[trans-4-(4-butylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)ethane

1-[trans-4-(4-pentylphenyl)cyclohexyl]-2-(2-chloropyridine-5-yl)ethane

1-[trans-4-(4-ethoxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-[trans-4-(4-propoxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-trans-4-(4-butoxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-[trans-4-(4-pentyloxyphenyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-(trans-4-ethylcyclohexyl)-2-(2-fluoropyridine-5-yl)ethane

1-(trans-4-propylcyclohexyl)-2-(2-fluoropyridine-5-yl)ethane

1-(trans-4-butylcyclohexyl)-2-(2-fluoropyridine-5-yl)ethane

1-(trans-4-pentylcyclohexyl)-2-(2-fluoropyridine-5-yl)ethane

1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl-2-(2-trifluoromethylpyridine-5-yl)ethane

1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)ethane

1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)ethane

1-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)ethane

1-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2-(2-trifluoromethylpyridine-5-yl)ethane

1-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]-2-(2-fluoropyridine-5-yl)ethane

1-(trans-4-ethylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)phenyl]-ethane

1-(trans-4-propylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)phenyl-ethane C124 N 159 I phenyl]-ethane

1-(trans-4-pentylcyclohexyl)-2-4-(2-chloropyridin-5-yl)phenyl]-ethane

1-(trans-4-hexylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)phenyl]-ethane

1-(trans-4-heptylcyclohexyl)-2-4-(2-chloropyridin-5-yl)phenyl]-ethane

Example 8

A suspension of 0,02 M oftrans-4-(trans-4-ethylcyclohexyl)cyclohexylbromide, 0,04 M of lithiumand 0,01 M of ZnBr₂ is stirred for 2 hours at about 10° with ultrasonic.0,02 M of 3-bromo-2,6-difluoropyridine and 0,1 g of Pd(Ph₃ P)₄ are addedand the mixture is stirred for 4 hours.

After customary work-up2,6-difluoro-3-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pyridine isobtained

The following compounds are obtained analogously:

2,6-difluoro-3-trans-4-(trans-4-methylcyclohexyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pyridine

6-chloro-3-[trans-4-(trans-4-ethylcyclohexyl)-cyclohexyl]pyridine

6-chloro-3-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]pyridine

6-chloro-3-[trans-4-(trans-4-butylcyclohexyl)-cyclohexyl]pyridine

6-chloro-3-[trans-4-(trans-4-pentylcyclohexyl)-cyclohexyl]pyridine

6-chloro-3-[trans-4-(trans-4-heptylcyclohexyl)-cyclohexyl]pyridine

6-trifluoromethyl-3-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethyl-3-trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethyl-3-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethyl-3-trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethyl-3-trans-4-(trans-4-hexylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethyl-3-[trans-4-(trans-4-heptylcyclohexyl)-cyclohexyl]pyridine

6-trifluoromethoxy-3-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethoxy-3-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethoxy-3-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pyridine

6-trifluoromethoxy-3-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pyridine

6-difluoromethoxy-3-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pyridine

6-difluoromethoxy-3-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pyridine

6-difluoromethoxy-3-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pyridine

6-difluoromethoxy-3-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pyridine

2,6-difluoro-3-(trans-4-ethylcyclohexyl)pyridine

2,6-difluoro-3-(trans-4-propylcyclohexyl)pyridine

2,6-difluoro-3-(trans-4-butylcyclohexyl)pyridine

2,6-difluoro-3-(trans-4-pentylcyclohexyl)pyridine

2,6-difluoro-3-[trans-4-(4-ethylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-propylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-butylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-pentylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-ethoxyphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-propoxyphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-butoxyphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-pentyloxyphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(4-octyloxyphenyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-[trans-4-(4-ethylphenyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-[trans-4-(4-propylphenyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-[trans-4-(4-butylphenyl)cyclohexyl]pyridine

6-chloro-2-fluoro-3-[trans-4-(4-pentylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(2-fluoro-4-ethylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(2-fluoro-4-propylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(2-fluoro-4-butylphenyl)cyclohexyl]pyridine

2,6-difluoro-3-[trans-4-(2-fluoro-4-pentylphenyl)cyclohexyl]pyridine

Example 9

Analogously to example 82-fluoro-5-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pyridine isobtained by reacting trans-4-(trans-4-ethylcyclohexyl)cyclohexylbromidewith 2-fluoro-5-bromopyridine.

The following compounds are obtained analogously:

2-fluoro-5-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(trans-4-octylcyclohexyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pyridine

2-trifluoromethyl-5-(trans-4-ethylcyclohexyl)-pyridine

2-trifluoromethyl-5-(trans-4-propylcyclohexyl)-pyridine

2-trifluoromethyl-5-(trans-4-butylcyclohexyl)-pyridine

2-trifluoromethyl-5-(trans-4-pentylcyclohexyl)-pyridine

2-trifluoromethoxy-5-(trans-4-ethylcyclohexyl)-pyridine

2-trifluoromethoxy-5-(trans-4-propylcyclohexyl)-pyridine

2-trifluoromethoxy-5-(trans-4-butylcyclohexyl)-pyridine

2-trifluoromethoxy-5-(trans-4-pentylcyclohexyl)-pyridine

2-difluoromethoxy-5-(trans-4-ethylcyclohexyl)-pyridine

2-difluoromethoxy-5-(trans-4-propylcyclohexyl)-pyridine

2-difluoromethoxy-5-(trans-4-butylcyclohexyl)-pyridine

2-difluoromethoxy-5-(trans-4-pentylcyclohexyl)-pyridine

2-fluoro-5-(trans-4-ethylcyclohexyl)-pyridine

2-fluoro-5-(trans-4-propylcyclohexyl)-pyridine

2-fluoro-5-(trans-4-butylcyclohexyl)-pyridine

2-fluoro-5-(trans-4-pentylcyclohexyl)-pyridine

2-fluoro-5-(trans-4-hexylcyclohexyl)-pyridine

2-fluoro-5-[trans-4-(4-ethylphenyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(4-propylphenyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(4-butylphenyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(4-pentylphenyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(4-ethoxyphenyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(4-propoxyphenyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(4-butoxyphenyl)cyclohexyl]pyridine

2-fluoro-5-[trans-4-(4-pentyloxyphenyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(4-ethylphenyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(4-propylphenyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(4-butylphenyl)cyclohexyl]pyridine

2-chloro-5-[trans-4-(4-pentylphenyl)cyclohexyl]pyridine

2-trifluoromethyl-5-[trans-4-(4-ethylphenyl)cyclohexyl]pyridine

2-trifluoromethyl-5-[trans-4-(4-propylphenyl)cyclohexyl]pyridine

2-trifluoromethyl-5-[trans-4-(4-butylphenyl)cyclohexyl]pyridine

2-trifluoromethyl-5-[trans-4-(4-pentylphenyl)cyclohexyl]pyridine

Example 10

A liquid crystalline medium consisting of

a) 90% of a mixture A consisting of

24% p-(trans-4-propylcyclohexyl)benzonitrile,

36% p-(trans-4-pentylcyclohexyl)benzonitrile,

25% p-(trans-4-heptylcyclohexyl)benzonitrile and 15%4-cyano-4'-(trans-4-pentylcyclohexyl)-biphenyl and

b) 10% 2,6-difluoro-3-[4-(trans-4-pentylcyclohexyl)phenylpyridine

has a clearing point of 71.2°.

Example 11

A liquid crystalline medium consisting of

a) 90% of a mixture A consisting of

22% p-(trans-propylcyclohexyl)-ethylbenzene,

20% p-(trans-propylcyclohexyl)-methoxybenzene,

15% p-(trans-propylcyclohexyl)-ethoxybenzene,

19% 4'-(trans-propylcyclohexyl)-4-ethylbiphenyl

14% 4'-(trans-pentylcyclohexyl)-4-ethylbiphenyl

5% bis-4,4'-(trans-propylcyclohexyl)biphenyl

5% 4'-(trans-4-propylcyclohexyl)-4-(trans-4-pentylcyclohexyl)-biphenyland

b) 10% of1-(trans-4-propylcyclohexyl)-2-[4-(2-chloropyridin-5-yl)-phenyl]-ethane

a clearing point of 77.1 ° C.

What is claimed is:
 1. Pyridine derivatives of the formula I ##STR12##wherein R¹ denotes alkyl with up to 12 carbon atoms wherein one or twonon-adjacent CH₂ -groups may also be replaced by --O--, --O--CO--,--CO--O-- and/or --CH═CH--,Y is F, Cl, --CF₃, --OCF₃ or OCHF₂, A¹ and A²in each case independently of one another are trans-1,4-cyclohexylene,wherein one or two non-adjacent CH₂ -groups may also be replaced by--O-- or --S--, or 1,4-phenylene which is unsubstituted or substitutedby one or more halogen atoms and/or nitrile and/or CH₃ groups, andwherein one or more CH groups may also be replaced by N, Z¹ and Z² ineach case independently of one another are --CH --CO--O--, --O--CO--,--CH₂ O--, --OCH₂ --, --C.tbd.C-- or a single bond, X is H, or in caseof Y=F or Cl, also F and n is 0, 1 or
 2. 2. Pyridine derivatives ofclaim 1, wherein X is H.
 3. Pyridine derivatives of claim 1, wherein Xis F.
 4. Pyridine derivatives of claim 1 wherein Y is F or Cl. 5.Pyridine derivatives of claim 1 or 3 wherein Y is F or Cl.
 6. Pyridinederivatives of claim 1 wherein Y is --OCF₃.
 7. Pyridine derivatives ofclaim 1 wherein Y is --CF₃.
 8. Pyridine derivatives of claim 1 wherein Yis --OCHF₂.
 9. Pyridine derivatives of claim 1, wherein R¹ denotes anunbranched alkyl radical of 2 to 7 carbon atoms.
 10. Pyridinederivatives of claims 1, wherein n is 0 or
 1. 11. Pyridine derivativesof claims 1, wherein Z¹ and Z² are each a single bond.
 12. Pyridinederivatives of claim 1, wherein Z² is --CO--O--, --CH or --C.tbd.C--.13. Liquid crystalline medium being a mixture of at least two compounds,characterized in that at least one compound is a pyridine derivativeaccording to claim
 1. 14. Liquid crystal display device, characterizedin that it contains a liquid crystalline medium according to claim 13.15. Electrooptical display device, characterized in that it contains aliquid crystalline medium according to claim 13.